The nature of the charges weren’t immediately known, the official told NBC News Justice Department correspondent Pete Williams, speaking on condition of anonymity. But because Angela Corey, the special prosecutor appointed by Florida Gov. Rick Scott to re-examine the case, previously announced that she wouldn’t take the case to a grand jury, first-degree murder is not an option.

Authorities in Sanford, Fla. — where Zimmerman, 28, a neighborhood watch volunteer, shot Martin, 17, on Feb. 26 — also began preparing for an announcement from Corey, NBC station WESH of Orlando reported. Seminole County sheriff’s deputies spent Wednesday morning setting up barricades along the booking area for new inmates at the county jail.

Martin’s father, Tracy Martin, said he was looking forward to Corey’s announcement.